LIMDs are typically small-sized leadless devices configured for direct implant within an organ, such as within a chamber of the heart. LIMDs are generally characterized by the following features: electrodes are affixed or mounted to a can or housing of the device and the entire device is attached or implanted within tissues or organs to be sensed or simulated. In the case of an LIMD for implant within the heart, such devices are typically implanted within the right ventricle (RV) of the heart for delivering pacing pulses to the RV, though LIMDs have also be provided or proposed for implant within other chambers such as the right atrium (RA.) LIMDs configured for implant within the heart to provide electrical pacing are often referred to as leadless pacemakers (LLPM). For generality, the term LIMD will be used herein since aspects of the present disclosure may be applicable to LIMDs for implant into other organs than the heart and for other purposes besides pacing.
LIMDs for implant within the heart are described, for example, in the following: U.S. Patent Application 2013/0123872 of Bornzin et al., entitled “Leadless Implantable Medical Device with Dual Chamber Sensing Functionality”; U.S. Patent Application 2013/0138006 of Bornzin et al., entitled “Single Chamber Leadless Intra-Cardiac Medical Device having Dual Chamber Sensing with Signal Discrimination”; U.S. Patent Application 2013/0116741 of Bornzin et al., entitled “Dual-Chamber Leadless Intra-Cardiac Medical Device with Intra-Cardiac Extension”; U.S. Patent Application 2013/0116740 of Bornzin et al., entitled “Single-Chamber Leadless Intra-Cardiac Medical Device with Dual-Chamber Functionality And Shaped Stabilization Intra-Cardiac Extension”; U.S. Patent Application 2013/0110219 of Bornzin et al., entitled “Unitary Dual-Chamber Leadless Intra-Cardiac Medical Device and Method of Implanting Same”; U.S. Patent Application 2013/0110127 of Bornzin et al., entitled “Multi-Piece Dual-Chamber Leadless Intra-Cardiac Medical Device and Method of Implanting Same”; U.S. Patent Application 2013/0116738 of Samade et al., entitled “Single Chamber Leadless Intra-Cardiac Medical Device with Dual-Chamber Functionality”; and U.S. Patent Application 2013/0116529 of Min et al., entitled “Leadless Intra-Cardiac Medical Device with Built-In Telemetry System.”
LIMDs for implant in the RV are usually placed in the RV apex or low RV septum near the apex. Typical examples of such devices have battery capacities that allow for about eight to ten years of pacing. This is deemed adequate but it would be better if the devices could last even longer because removing the device for replacement has various risks and in some cases might be quite challenging. As such, should the battery of an LIMD in the RV become depleted, it might be necessary to implant a second LIMD or implant a conventional pacemaker with leads into the heart, with the various risks, costs and potential complications associated therewith.
Accordingly, it would be desirable to provide systems and methods for reducing the power consumption of LIMDs so as to extend their usable lifetimes, particularly for use with LIMDs for implant within the heart, and it is to these ends that at least some aspects of the invention are directed.